This invention relates to pushbutton selector switches of the type wherein a pair of pushbuttons housed in a common housing are depressible to operate respective individual switch contact sets to an ON condition. An interlock is provided to prevent depression of both buttons simultaneously. A latch mechanism is provided to latch a respective pushbutton in a depressed position, thereby retaining the associated contact set in a closed position. A third pushbutton located between the aforementioned pair of pushbuttons is depressible to release the latch mechanism.
Switches of the aforementioned type have been known heretofore. The pushbutton switch shown in U.S. Pat. No. 4,392,029 issued Jul. 5, 1983 to William J. Schaad et al and in U.S. Pat. No. 4,447,688 issued May 8, 1984, a division of 4,392,029, discloses various arrangements of pushbuttons which may be interlocked or latched, some of which include a separate release button. A deflectable arm molded integral with the housing is disposed between and parallel to a pair of adjacent pushbuttons for engagement by projections on the pushbuttons to deflect the member into the path of one pushbutton upon depression of the other, thereby providing an interlock between adjacent pushbuttons, preventing both pushbuttons from being depressed at the same time. The same arm is provided with latch surfaces as are the projections on the adjacent pushbuttons whereby depression of one pushbutton causes the arm to engage that pushbutton and latch it depressed until the other pushbutton is depressed to release the latch. This switch can provide latching or interlocking between an adjacent pair of buttons only and not between a widely spaced pair of pushbuttons. The projections on the pushbuttons bear downward on the deflectable arm to place the arm under compression. The projections and the upper surfaces of the arm are angled, providing sliding cam surfaces which deflect the arm at a right angle direction change for the movement of the pushbutton.
Another switch of the aforementioned type is that shown in U.S. Pat. No. 4,544,810 issued Oct. 1, 1985 to Edmund M. Butterworth and assigned to the assignee of this invention. This switch comprises a pair of depressible outer pushbuttons alternately operable by a sliding interlock structure cammed for movement at right angles to the movement of the pushbutton by cam surfaces on the respective pushbuttons and interlock. A latch system comprises a centrally disposed release pushbutton having an actuator pivotally mounted thereon and a pair of latch members rotatably mounted in the housing on opposite sides of the actuator. The latch members engage both the actuator and a respective adjacent outer pushbutton to hold the release pushbutton depressed against a spring bias. Depression of an outer pushbutton aligns a shoulder on the outer pushbutton with a projection on an adjacent latch member, permitting the latch member to be rotated over the shoulder to a position of interference with the depressed outer pushbutton and permitting the spring to bias the release pushbutton to an extended position. Depression of the release pushbutton carries the actuator beyond a release point of the latch to reset the system. This switch utilizes a 90 degree or right angle direction change in sliding movement for the interlock member and an inter-cooperating multiple part latch system which provides interference to movement of an outer pushbutton member as opposed to true latching engagement with that member.
U.S. Pat. No. 4,701,578 issued Oct. 20, 1987 to J. J. Keranen et al and assigned to the assignee of this invention is an improvement over the Butterworth patent. The outermost pair of pushbuttons in this switch are interlocked to prevent simultaneous depression and are latched in the depressed position by a pair of sliding plates which are cammed for movement at right angles to movement of the pushbuttons by cooperating cam surfaces on the pushbuttons and the slide plates. The slide plates drive rotatably mounted contact actuators. The sliding movement and right angle camming action in this and the aforementioned switches creates high amounts of friction and potential window locking of the elements in operation.
U.S. Pat. No. 3,560,677 issued Feb. 2, 1971 and also assigned, by mesne assignments, to the assignee of this invention, discloses a pushbutton selector switch having the outer pushbuttons interlocked against simultaneous contact operation. An interlock bar is pivotally mounted on a centrally disposed OFF pushbutton. Opposite ends of the interlock bar underlie the respective outer pushbuttons. Depression of bout outer pushbuttons causes the interlock bar to depress the central pushbutton, thereby opening a set of normally closed contacts to disconnect electrical power to the switch before both outer contacts close.
While interlocking pushbutton selector switches of the aforementioned type have been useful for their intended purposes, this invention relates to improvements thereover, and more particularly to improvements over U.S. Pat. No. 4,701,578, which patent is incorporated herein by reference.